org.apache.commons.math.ode
Class AbstractIntegrator

java.lang.Object
  extended by org.apache.commons.math.ode.AbstractIntegrator
All Implemented Interfaces:
FirstOrderIntegrator, ODEIntegrator
Direct Known Subclasses:
AdaptiveStepsizeIntegrator, RungeKuttaIntegrator

public abstract class AbstractIntegrator
extends java.lang.Object
implements FirstOrderIntegrator

Base class managing common boilerplate for all integrators.

Since:
2.0
Version:
$Revision: 811827 $ $Date: 2009-09-06 11:32:50 -0400 (Sun, 06 Sep 2009) $

Nested Class Summary
private static class AbstractIntegrator.EndTimeChecker
          Specialized event handler to stop integration.
 
Field Summary
private  FirstOrderDifferentialEquations equations
          Differential equations to integrate.
private  int evaluations
          Number of evaluations already performed.
protected  CombinedEventsManager eventsHandlersManager
          Events handlers manager.
private  int maxEvaluations
          Maximal number of evaluations allowed.
private  java.lang.String name
          Name of the method.
protected  java.util.Collection<StepHandler> stepHandlers
          Step handler.
protected  double stepSize
          Current stepsize.
protected  double stepStart
          Current step start time.
 
Constructor Summary
protected AbstractIntegrator()
          Build an instance with a null name.
  AbstractIntegrator(java.lang.String name)
          Build an instance.
 
Method Summary
protected  CombinedEventsManager addEndTimeChecker(double startTime, double endTime, CombinedEventsManager manager)
          Add an event handler for end time checking.
 void addEventHandler(EventHandler function, double maxCheckInterval, double convergence, int maxIterationCount)
          Add an event handler to the integrator.
 void addStepHandler(StepHandler handler)
          Add a step handler to this integrator.
 void clearEventHandlers()
          Remove all the event handlers that have been added to the integrator.
 void clearStepHandlers()
          Remove all the step handlers that have been added to the integrator.
 void computeDerivatives(double t, double[] y, double[] yDot)
          Compute the derivatives and check the number of evaluations.
 double getCurrentSignedStepsize()
          Get the current signed value of the integration stepsize.
 double getCurrentStepStart()
          Get the current value of the step start time ti.
 int getEvaluations()
          Get the number of evaluations of the differential equations function.
 java.util.Collection<EventHandler> getEventHandlers()
          Get all the event handlers that have been added to the integrator.
 int getMaxEvaluations()
          Get the maximal number of functions evaluations.
 java.lang.String getName()
          Get the name of the method.
 java.util.Collection<StepHandler> getStepHandlers()
          Get all the step handlers that have been added to the integrator.
protected  boolean requiresDenseOutput()
          Check if one of the step handlers requires dense output.
protected  void resetEvaluations()
          Reset the number of evaluations to zero.
protected  void sanityChecks(FirstOrderDifferentialEquations ode, double t0, double[] y0, double t, double[] y)
          Perform some sanity checks on the integration parameters.
protected  void setEquations(FirstOrderDifferentialEquations equations)
          Set the differential equations.
 void setMaxEvaluations(int maxEvaluations)
          Set the maximal number of differential equations function evaluations.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface org.apache.commons.math.ode.FirstOrderIntegrator
integrate
 

Field Detail

stepHandlers

protected java.util.Collection<StepHandler> stepHandlers
Step handler.


stepStart

protected double stepStart
Current step start time.


stepSize

protected double stepSize
Current stepsize.


eventsHandlersManager

protected CombinedEventsManager eventsHandlersManager
Events handlers manager.


name

private final java.lang.String name
Name of the method.


maxEvaluations

private int maxEvaluations
Maximal number of evaluations allowed.


evaluations

private int evaluations
Number of evaluations already performed.


equations

private transient FirstOrderDifferentialEquations equations
Differential equations to integrate.

Constructor Detail

AbstractIntegrator

public AbstractIntegrator(java.lang.String name)
Build an instance.

Parameters:
name - name of the method

AbstractIntegrator

protected AbstractIntegrator()
Build an instance with a null name.

Method Detail

getName

public java.lang.String getName()
Get the name of the method.

Specified by:
getName in interface ODEIntegrator
Returns:
name of the method

addStepHandler

public void addStepHandler(StepHandler handler)
Add a step handler to this integrator.

The handler will be called by the integrator for each accepted step.

Specified by:
addStepHandler in interface ODEIntegrator
Parameters:
handler - handler for the accepted steps
See Also:
ODEIntegrator.getStepHandlers(), ODEIntegrator.clearStepHandlers()

getStepHandlers

public java.util.Collection<StepHandler> getStepHandlers()
Get all the step handlers that have been added to the integrator.

Specified by:
getStepHandlers in interface ODEIntegrator
Returns:
an unmodifiable collection of the added events handlers
See Also:
ODEIntegrator.addStepHandler(StepHandler), ODEIntegrator.clearStepHandlers()

clearStepHandlers

public void clearStepHandlers()
Remove all the step handlers that have been added to the integrator.

Specified by:
clearStepHandlers in interface ODEIntegrator
See Also:
ODEIntegrator.addStepHandler(StepHandler), ODEIntegrator.getStepHandlers()

addEventHandler

public void addEventHandler(EventHandler function,
                            double maxCheckInterval,
                            double convergence,
                            int maxIterationCount)
Add an event handler to the integrator.

Specified by:
addEventHandler in interface ODEIntegrator
Parameters:
function - event handler
maxCheckInterval - maximal time interval between switching function checks (this interval prevents missing sign changes in case the integration steps becomes very large)
convergence - convergence threshold in the event time search
maxIterationCount - upper limit of the iteration count in the event time search
See Also:
ODEIntegrator.getEventHandlers(), ODEIntegrator.clearEventHandlers()

getEventHandlers

public java.util.Collection<EventHandler> getEventHandlers()
Get all the event handlers that have been added to the integrator.

Specified by:
getEventHandlers in interface ODEIntegrator
Returns:
an unmodifiable collection of the added events handlers
See Also:
ODEIntegrator.addEventHandler(EventHandler, double, double, int), ODEIntegrator.clearEventHandlers()

clearEventHandlers

public void clearEventHandlers()
Remove all the event handlers that have been added to the integrator.

Specified by:
clearEventHandlers in interface ODEIntegrator
See Also:
ODEIntegrator.addEventHandler(EventHandler, double, double, int), ODEIntegrator.getEventHandlers()

requiresDenseOutput

protected boolean requiresDenseOutput()
Check if one of the step handlers requires dense output.

Returns:
true if one of the step handlers requires dense output

getCurrentStepStart

public double getCurrentStepStart()
Get the current value of the step start time ti.

This method can be called during integration (typically by the object implementing the differential equations problem) if the value of the current step that is attempted is needed.

The result is undefined if the method is called outside of calls to integrate.

Specified by:
getCurrentStepStart in interface ODEIntegrator
Returns:
current value of the step start time ti

getCurrentSignedStepsize

public double getCurrentSignedStepsize()
Get the current signed value of the integration stepsize.

This method can be called during integration (typically by the object implementing the differential equations problem) if the signed value of the current stepsize that is tried is needed.

The result is undefined if the method is called outside of calls to integrate.

Specified by:
getCurrentSignedStepsize in interface ODEIntegrator
Returns:
current signed value of the stepsize

setMaxEvaluations

public void setMaxEvaluations(int maxEvaluations)
Set the maximal number of differential equations function evaluations.

The purpose of this method is to avoid infinite loops which can occur for example when stringent error constraints are set or when lots of discrete events are triggered, thus leading to many rejected steps.

Specified by:
setMaxEvaluations in interface ODEIntegrator
Parameters:
maxEvaluations - maximal number of function evaluations (negative values are silently converted to maximal integer value, thus representing almost unlimited evaluations)

getMaxEvaluations

public int getMaxEvaluations()
Get the maximal number of functions evaluations.

Specified by:
getMaxEvaluations in interface ODEIntegrator
Returns:
maximal number of functions evaluations

getEvaluations

public int getEvaluations()
Get the number of evaluations of the differential equations function.

The number of evaluations corresponds to the last call to the integrate method. It is 0 if the method has not been called yet.

Specified by:
getEvaluations in interface ODEIntegrator
Returns:
number of evaluations of the differential equations function

resetEvaluations

protected void resetEvaluations()
Reset the number of evaluations to zero.


setEquations

protected void setEquations(FirstOrderDifferentialEquations equations)
Set the differential equations.

Parameters:
equations - differential equations to integrate
See Also:
computeDerivatives(double, double[], double[])

computeDerivatives

public void computeDerivatives(double t,
                               double[] y,
                               double[] yDot)
                        throws DerivativeException
Compute the derivatives and check the number of evaluations.

Parameters:
t - current value of the independent time variable
y - array containing the current value of the state vector
yDot - placeholder array where to put the time derivative of the state vector
Throws:
DerivativeException - this exception is propagated to the caller if the underlying user function triggers one

sanityChecks

protected void sanityChecks(FirstOrderDifferentialEquations ode,
                            double t0,
                            double[] y0,
                            double t,
                            double[] y)
                     throws IntegratorException
Perform some sanity checks on the integration parameters.

Parameters:
ode - differential equations set
t0 - start time
y0 - state vector at t0
t - target time for the integration
y - placeholder where to put the state vector
Throws:
IntegratorException - if some inconsistency is detected

addEndTimeChecker

protected CombinedEventsManager addEndTimeChecker(double startTime,
                                                  double endTime,
                                                  CombinedEventsManager manager)
Add an event handler for end time checking.

This method can be used to simplify handling of integration end time. It leverages the nominal stop condition with the exceptional stop conditions.

Parameters:
startTime - integration start time
endTime - desired end time
manager - manager containing the user-defined handlers
Returns:
a new manager containing all the user-defined handlers plus a dedicated manager triggering a stop event at entTime


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